I have a 1957 Ford Distributor and a Pertronix I in my TBird. I also have a Pertronix 1.5 ohm coil with no external resistor. I experienced an intermittent miss that went away when I disconnected the O/D wire. It did not blow the Pertronix Unit. The O/D kickdown switch is an open switch located in a place where corrosion, oil and grim can get to it. The way I drive my car, I have no use for kick down. Downshifting when I want to pass works for me. Since disconnecting the O/D wire, my car has been running for over a year with no issues. If you blow the Pertronix unit, you are dead in the water. You can carry an extra unit or reinstall your points. To me, having a working kick down circuit is not worth the risk that I will be sitting on the side of the road with a flash light and a screw driver.
To be honest, I have never experienced a Pertronix unit failure and I have used a bunch of them over the years. At the same time, I have experienced numerous failures of Chinese points and condensers.